The RuntimeExpressionResolver is holding the lock on the collection for the entire resolution of the expression step, this means there is a risk of deadlock across multiple threads

https://github.com/wildfly/wildfly-core/blob/main/server/src/main/java/org/jboss/as/server/RuntimeExpressionResolver.java#L55-L57

We need to double check but from our discussions we feel it was likely this locking was to protect the iterator from modifications to the underlying collection but we can handle that in a different way, the individual extensions are responsible for their own locking requirements.